Polyorganophosphazenes comprise a linear or cyclic chain of ##STR1## units in which the P atom is substituted with 2 organo groups which may be the same or different. Typical organo substituents are phenoxy, alkylphenoxy, halphenoxy, alkoxyphenoxy, alkoxy, polyalkoxy, haloalkoxy and the like. Typical polyaryloxyphosphazenes are disclosed in U.S. Pat. No. 3,853,794 and typical polyfluoroalkoxyphosphazenes are taught in U.S. Pat. No. 3,515,688. Mixed aryloxy-fluoroalkoxy substituted polyphosphazenes are disclosed in U.S. Pat. No. 3,700,629.
Linear and cyclic polyorganophosphazenes are soluble in solvents such as tetrahydrofuran (THF), cyclohexane, benzene and toluene but can be cured (i.e., cross-linked) to an insoluble elastomer. Rose et al. U.S. Pat. No. 3,888,799 disclose polyfluoroalkoxyphosphazenes containing unsaturated aliphatic groups such as allyloxy that can be cross-linked by peroxide curing agents. Vicic et al. U.S. Pat. No. 3,945,966 mentions that polyfluoroalkoxyphosphazenes containing isoeugenol moieties (i.e., 2-methoxy-4-propenylphenoxide) may be peroxide cured. This appears to be based on the research described in Reynard et al. "Evaluation of Poly (Fluoroalkoxyphosphazene) Elastomers and Plastics," Final Report, Contract No. DAAG46-73-C-0215, AMMRC CTR 74-18.
Kyker et al. U.S. Pat. No. 3,970,533 disclose polyfluoroalkoxyphosphazenes having some alkenylphenoxy substituents, especially ortho-allylphenoxy, which can be cured by peroxides, radiation or conventional sulfur vulcanization. Dieck et al. U.S. Pat. No. 4,113,670 disclose polyaryloxyphosphazenes which have alkenylaryloxy groups (e.g., ortho-allyphenoxy, eugenoxy, etc.) which can be cured by peroxides or sulfur.
Cheng U.S. Pat. No. 4,116,785 discloses certain non-fluorinated alkoxy and/or aryloxy-substituted polyphosphazenes which also contain olefinic substituents such as ortho-allylphenoxy groups which can be cured by conventional sulfur vulcanization or by radiation.